Field of the Invention
The present invention relates to a device for purifying exhaust gas, and more particularly, to a device for purifying exhaust gas configured for reducing harmful materials in exhaust gas using a Linde Type A (LTA) zeolite catalyst with an improved high-temperature performance.
Description of Related Art
In general, an exhaust system of an engine includes an exhaust gas post-processing device including a diesel oxidation catalyst (DOC), a diesel particulate matter filter (DPF), a selective catalyst reduction (SCR) and a lean NOx trap (LNT) catalyst to reduce carbon monoxide (CO), hydrocarbons (HC), a particulate matter, nitrogen oxide (NOx), and the like which are pollutants included in the exhaust gas.
The DOC may oxidize total hydrocarbon and carbon monoxide in the exhaust gas and oxidize nitrogen monoxide to nitrogen dioxide.
The DPF may collect a particulate material included in the exhaust gas and purify the particulate material through a chemical conversion process.
Further, in the SCR, a reducing agent (urea) injected in a stream direction of the exhaust gas through an injector is converted into ammonia (NH3) by heat of the exhaust gas, and as a catalytic reaction of nitrogen oxide and ammonia in exhaust gas by the SCR catalyst, nitrogen oxide is reduced to nitrogen gas (N2) and water (H2O).
In addition, recently, as emissions regulations for the vehicle are enhanced, improvement of a nitrogen oxide purification performance for the SCR system is required and particularly, a technique for reducing nitrogen oxide in the non-operating region of the SCR during a cold start is required.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.